324 THE BLOODVESSELS OF THE EYE, BY TH. LEBER. 



through the vence vorticosce, a portion only of the blood of the 

 ciliary muscle discharging itself externally through the small 

 anterior ciliary veins; which portion is far inferior to the 

 other in importance. 



(1.) ARTERIES OF THE CHOROID. 



The small trunks of the short ciliary arteries in the pos- 

 terior segments of the choroid lie at first in the most superficial 

 layers of the membrane, surrounded by a loose, and for the 

 most part darkly pigmented tissue. As they pass forwards 

 they are very tortuous, and, dividing dichotomously, gradu- 

 ally dip into the deeper layers. The finest branches break up 

 into the capillary plexus which covers uniformly the whole 

 internal surface of the choroid, forming the so-called chorio- 

 capillaris. The ramifications which run forward are differ- 

 entiated from the veins by their straighter course, whilst the 

 finer branches found in the neighbourhood of the optic nerves 

 are, like those of the veins, very tortuous. This circumstance, 

 together with the large number of vessels here present, gives the 

 whole membrane the appearance, in well injected specimens, of 

 being an inextricable convolute of minute vessels. 



Besides the branches which break up into capillaries, there 

 are no other branches,* as was formerly admitted, which directly 

 discharge themselves into the veins. The belief in the pre- 

 sence of the latter was dependent on illusory appearances, 

 which were easily produced in the methods of opaque injection 

 formerly employed, but which are completely removed by the 

 use of coloured transparent injections. f 



The short ciliary arteries break up completely into the 

 capillary plexus of the choroid, and give off no branches for- 



* Briicke, Anatomische Beschreibung des menschlichen Augapfels (Anato- 

 mical description of the Eye of Man), p. 14. Berlin, 1847. 



f Th. Leber, Anatomische Untersuchungen uber die Blutgefasse des 

 menschlichen Auge (Anatomical researches on the bloodvessels of the 

 Eye of Man), Denkschrift der A kademie zu Wien, Band xxiv. ; Math. 

 Naturwissensch. Classe, p. 301 ; also Untersuchungen uber den Verlauf und 

 Zusammerihang der Gefdsse im menschlichen Auge (Researches on the 

 course and communications of the vessels of the Eye in Man), Arcliiv fur 

 Optiihalmologie, Band xi., p. 15. 



